1. Field of the Invention
The present invention relates generally to management of trains operating within a track network, and in particular to a short headway communications based train control system for use in establishing a local communication link between two or more trains within the track network, and creating a virtual train that can be managed and controlled within this track network.
2. Description of the Related Art
As is known, and at any given time within a complex track network, multiple trains are operating and traversing the tracks. These trains are normally in communication with a central dispatch office, which issues movement and other control authorities to ensure safe operations of all of these trains in the track network. Further, each individual train may have an on-board communication and control system that facilitates the safe operation of the train in its local territory within the network. For example, these trains may communication with wayside devices through a radio link or a track-based communication link. In this manner, each individual train may be controlled and safely operated.
With reference to conventional fixed block signal systems, the distance between two following trains is limited, and based upon block sections, which ensure safe train separation. A “three aspect” signal system, as is presently widely deployed, requires two non-occupied block sections separating trains in following moves on the same track. In freight operations, these block sections are typically on the order of one mile of separation. Accordingly, following trains are normally operated with a following movement train separation of at least two to four miles, since the system cannot differentiate position in any greater precision than the fixed block length. Further, systems can be deployed with progressively smaller block sections, but the cost of installing the required wayside equipment, i.e., a wayside device for each block section, increases to the point where it is generally not economically feasible.
“Moving block” systems are also known and have been deployed in high-density transit applications, e.g., subways, which are generally based on a central office system that tracks each train and maintains a safe headway using centralized logic (i.e., a control unit at the central office). Such systems require a high-bandwidth data network between vehicles and the central office, as well as a high-cost and centralized failsafe computing environment and communications network. As is known, these “moving block” systems employed in the subway environment have not been effectively implemented in connection with freight train operations (which require a complex and widespread track system), primarily based upon the associated costs of implementation.
The progression from conventional signal systems to new Communications-Based Train Control (CBTC) systems has been based upon maintaining fixed block control, even without the need for wayside track circuits to define the blocks. For example, even in non-signal (or “dark”) territory, by utilizing Track Warrant Control (TWC) procedures, trains are dispatched based upon an authority limited to a “virtual” block section, which is clear of other trains.
The Wabtec Electronic Train Management System (ETMS) is one example of a CBTC system, and has been applied as an overlay to Conventional Train Control (CTC) systems, as well as non-signal (TWC) territory. Further, ETMS has been expanded to support standalone vital applications (V-ETMS), which have the capability to operate as stand-alone failsafe control systems. Accordingly, this V-ETMS would be considered a replacement of both the conventional signal system and the track warrant control procedures. Such CBTC systems, including the Wabtec V-ETMS, may be used in one implementation of the present invention.
For example, the V-ETMS is operable to define progressively smaller “virtual” blocks as a means to support reduced headway operations. This provides system operation similar to that of a moving block system, as applied in metro-transit, e.g., subway, operations. However, such an implementation places an increased bandwidth demand on the communications network, which would require a significant investment in the upgrade of the communications infrastructure. Therefore, and in one aspect of the present invention, it is an object to provide such V-ETMS or CBTC functionality to support short headway train operations, without the need for a new or significantly upgraded communications infrastructure.
There are also known systems related to Distributed Power (DP) trains, which are supported by communication between locomotives, including radio-based communications for conventional trains and wire line-based communications for ECP-brake trains. The above-discussed limitations and drawbacks relating to fixed block signal systems have lead to railroads requiring an increased length in the trains as the best manner of increasing capacity. A DP train may be considered as operating two trains hard-coupled together (or as a zero-headway operation). However, one of the operating drawbacks associated such DP trains is the extra switching time relating to setting up the train for departure, as well as the need to break-up the train at the destination yard to fit within available tracks. This has lead to DP train operation largely limited to long unit trains, which can cycle without the need to be split on either end of the trip. Therefore, and in another aspect of the present invention, it is a further object to provide the ability to operate trains with short headway in an operation similar to a DP train setting, where the capacity advantages of long trains can be gained, while maintaining the flexibility of switching train sections or having diverging routes.